Since we're living in a Golden Age of astronomical discoveries-- hard to believe that it was only a few years ago that extrasolar planets were technically theoretical and now we've got almost nine hundred on the books-- I thought we could use a thread in which to post those discoveries. When I finally broke down and got an iPhone a couple of months ago, I found a cool app that alerts me whenever a new planet is confirmed.

Of course, the most interesting planets (mostly) are the ones that fall into their star's habitable zone, and this app has a nice graphic feature that superimposes a green area over the map of the solar system in question to denote the habitable zone, and also compares it to the orbits of the planets in our solar system. I'll start by posting the most recent announcement that came through and will go back and fill in prior announcements as time goes on. Everyone else, of course, should chime in with their own news.

Oh, one recent ultra-cool discovery that doesn't fall into the potentially life-bearing category was the planet discovered at Alpha Centauri B. If you haven't heard of it, it is not only orbiting our nearest stellar neighbor, but it is also the smallest extra-solar planet found to date, at about 1.13 Earth masses. Sadly, it is in a very tight orbit, closer than Mercury, and so is not a likely candidate for life. But, still-- Alpha Centauri!

So, the news I will post today concerns the star Gliese 163, which is 48.9 light years away and has a stellar mass of .40 of our sun, which means that its habitable zone is very close. Two super Earths have been discovered, Gliese 163 b, which is 11.10 Earth masses and has a year of 8.63 days and Gliese 163 c, which is 6.90 Earth masses and has a year of 25.63 days. The outer edge of the habitable zone is about at the Mercury orbit. The b planet is way inside the inner edge of the zone, but c is right at the edge, and has a slightly eccentric orbit that takes it from barely there to comfortably inside. Radius, density and surface gravity info are not available (they seldom are).

This is how the app describes the planet:

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The HARPS team announced the discovery of a planetary system around the star Gliese 163 at this year's IAU conference. Gliese 163 c lies within the habitable zone for a wide range of albedo values and has an equilibrium temperature of 60C (140F). The scientific paper is currently undergoing peer review.

Sounds like a good prospect, unless it has succumbed to a runaway greenhouse effect.

HD 10647 b orbits a star 11% more massive than the sun and is 56.4 light years away. It is a gas giant just slightly smaller than Jupiter (.94%). It has a pretty eccentric orbit, which takes it from the comfortable middle of the habitable zone to well outside, and a year of 989.20 days (2.7 years)-- which means it spends more than a year outside the habitable zone each orbit. If there is any complex life on this planet's moons, I imagine they are all big on hibernation.

HD 30562 b is a gas giant of 1.37 Jupiter masses and an orbital period of 1159 days (about 3.2 years). It's host star is 1.23 solar masses and is 86.4 light years away. The habitable zone of this star extends from just outside the orbit of Earth to past the asteroid belt. This planet's orbit is hugely eccentric, taking it from inside the orbit of Venus to nearly the orbit of Jupiter. So while it spends about half it's time in the habitable zone, it spends the other half experiencing extremes of heat and cold-- I doubt if either the planet or any of its satellites are a good bet for life.

HD 196050 A b is a gas giant of 2.83 Jupiter masses and a year of 3.6 Earth years. Its star is 1.17 solar masses and is 153.1 light years away. Like yesterday's planet, today's is pretty eccentric, taking it from comfortably in the middle of the habitable zone to a good way outside it for half its orbit. It's not quite as bad as yesterday's, though, but still not a great bet for life.

This is a cool thread. I just haven't been commenting because I believe that our "sample of one" NECESSARILY gives us a skewed view of what is habitable, and our only slightly larger sample of local climates gives us a necessarily skewed view of what might exist in a given "zone" There are (we now find) places on Mercury where Earth microorganisms might survive or even evolve -- and who knows what native Mercurian microbes might be like. The same plausibly applies to all the inner planets except Venus and a few known gas giant moons, and "who knows what might have evolved there" applies everywhere, with our current limited knowledge.

The exoplanets that interest me most at present are "rogue planets" or Class Y (or maybe even T) dwarfs: we've recently started to find that these cool, and almost impossible to see, bodies are much more common than ever imagined --apparently more common than ALL "luminous" stars combined-- and this may turn interstellar space from multi-lightyear stretches of featureless waste to perhaps a giant void studded with "gas stations" and "warm oases" where we could refuel and set up habitable waystations with little more than current technology -- in, theory in my lifetime, but more realistically in scant centuries with no wishful thinking.

Just 1-2 brown dwarves/rogues between us and the Centauri would allow us to begin planning expeditions today, though [even under the most optimistic, motivated scheme] it might take a century or more to bootstrap Outer Planet, Oort Cloud and Rogue planet waystations to mount the first trans-stellar conventional-thrust manned mission.

This could also explain the MIssing Mass [Dark Matter] Problem, eliminating most of the problems that have caused physicists to populate their theoretical bestiary with MACHOs, WIMPs, Exotic Matter and Energy, etc. (while that might rob us of the Alcubierre Warp drive, such technology would be an unforeseeable distance in the future, even if exotic matter and energy exist, while "waystations" are directly foreseeable)

I just haven't been commenting because I believe that our "sample of one" NECESSARILY gives us a skewed view of what is habitable, and our only slightly larger sample of local climates gives us a necessarily skewed view of what might exist in a given "zone"

I agree. But with nearly 900 known Exoplanets and counting, I'm going to use the principle of mediocrity to winnow them down. It's very possible that hot Super-Jupiters in remote orbits have life-bearing Europas or Medeas (from that Harlan Ellison anthology), but that's speculative-- and even more extreme environments are even more speculative-- but if there's a planet in the habitable zone above a certain size, I think we're almost guaranteed a life-bearing world (whether that world has anything more complex than single-celled organisms is another question).

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The exoplanets that interest me most at present are "rogue planets" or Class Y (or maybe even T) dwarfs: we've recently started to find that these cool, and almost impossible to see, bodies are much more common than ever imagined --apparently more common than ALL "luminous" stars combined-- and this may turn interstellar space from multi-lightyear stretches of featureless waste to perhaps a giant void studded with "gas stations" and "warm oases" where we could refuel and set up habitable waystations with little more than current technology -- in, theory in my lifetime, but more realistically in scant centuries with no wishful thinking.

This wouldn't surprise me at all. It would fall in line with Asimov's "Law of the Numerous Small" (or words to that effect). And it's not impossible that a large rogue planet could have living things somewhere in its interior.

Nonny, on 06 December 2012 - 09:06 AM, said:

Informative and interesting. And very cool app!

Thank you. And, yeah, this is my favorite app. I just found out it was created by the team at Arecibo's Planetary Habitability Laboratory. They also have a web page that lists all know potentially habitable planets-- their list is up to seven. Apparently their standards are even more conservative than mine.

HD 142 A b is a gas giant 1.25 Jupiter masses with a year of 349.7 days orbiting a star of 1.15 solar masses. It has a slightly eccentric orbit, carrying it from just at the inner fringe of the habitable zone to comfortably within it (just outside the orbit of Venus to just outside the orbit of Earth). Any large moons would be quite a good bet for life.

And today's planet actually is 16 Cygni B b. It is a gas giant of 1.68 Jupiter masses and it is 69.8 light years from Earth (the star is almost identical in size to the sun). It's another planet with a highly eccentric orbit that takes it through the habitable zone, but also brings it well within and well outside (from inside the orbit of Venus to around the asteroid belt), so it is a long shot for life. Of interest, according to my app, is that a radio message was sent to this star in 1999 and will arrive in 2069 (good deal-- I'll only be 108).

And here's one with a more interesting name: Upsilon Andromedae A d is a gas giant of 10.19 Jupiter masses. The star is 1.27 times the mass of the sun and is 43.9 light years away. There are four known planets in the solar system. This one's orbit is somewhat eccentric, taking it from the comfy middle of the habitable zone to slightly outside it for part of its orbit-- doesn't seem like a deal breaker for life, but any habitable moons would have an interestingly changeable climate. Coincidentally, the next planet out, Upsilon Andromeda A e is almost exactly the size of Jupiter and its orbit matches almost exactly as well.

Okay, enough with the gas giants for a while. Today we have a Super-Earth: HD 40307 g. This planet orbits a star with a mass of .77 of our sun which is 41.7 light years from Earth and there are at least five planets in its solar system. The planet has a mass of 7.10 Earths and an orbital period of 197.8 days. It's somewhat eccentric orbit takes it from just at the inner edge of the habitable zone (about at the orbit of Mercury) to right comfortably in the middle (right around Venus). It could be a candidate for life-- on the other hand, it could be a candidate for a runaway greenhouse effect.

Another Super-Earth for you: HD 20794 d is 4.8 Earth masses and lies 19.8 light years away around a star that is .7 solar masses. It's year is equal to 90.31 days. There are three known planets in its solar system, all of them Super Earths-- the other two are way inside the habitable zone. Planet d is just at the inner edge of the habitable zone (about at the orbit of Mercury) and has a nearly perfect circular orbit (as do the other two). This is a prime candidate for a living world, although it could also be at risk for a runaway greenhouse effect.

Today's planet is another Super-Earth: Gliese 667C c is 22.7 light years from Earth. It is 4.5 times the mass of Earth and there are a total of two known planets in its solar system. The star is .33 solar masses and is part of a triple star system. The planet is well inside the orbit of Mercury and has an orbit of 28 days, but is comfortably in the middle of the habitable zone. According to the app, it receives about 10% less solar energy than Earth. In my opinion, this is about as sure a bet as it gets for life.

Today's Exoplanet is Kepler-35 (AB) b, a mini gas giant (or maxi terrestrial) that orbits a close binary an unlisted distance from Earth. The first star is 89% of the sun's mass and the second is 81%, leaving the habitable zone somewhat closer than it is in our system (although Earth would be smack dab in the middle). This planet is just inside the orbit of Venus and has a year of 131.46 days and that puts it comfortably inside the inner edge of the zone. That must be an interesting sky, huh? The mass of the planet is 13% of Jupiter, which my calculations (correct me if I'm wrong) tell me is 41.3 times the mass of Earth. Pretty big and probably tough to launch spaceships from if there are any spaceflight aficianados there, but it looks to me like a good bet for a thriving ecology. And there's always the possibility of large moons, as well.

^^ Thanks. I'm glad you're enjoying it. This is pretty exciting to me. I think it won't be long before we discover evidence of life on another world.

Today's planet is gas giant HD 62509 b, 33.7 light years from Earth, orbiting a star almost half again as massive as the sun. It has a nearly perfect circular orbit just outside the orbit of Mars, which in this system is just at the inner edge of the habitable zone. Its mass is 2.9 times that of Jupiter and its year is 589.64 days long. Any chance of life here would probably be on large moons of the planet and large moons are probably a given with a planet this massive. Another thought has just occurred to me-- with planets this large there should be correspondengly large LaGrange zones. I wonder if it would be possible for a Super-Jupiter to have an Earth-sized "Trojan" (stop snickering, you).

Today's Exoplanet is a gas giant half the size of Jupiter orbiting a star 197.3 light years away. It is the only known planet in this system so far. The star is .93 times the size of our sun, so the habitable zone is just about the same as ours, just a little closer. HD 99109 b has just a slightly eccentric orbit, but it is almost exactly where Earth is in our system. Any large moons would be perfectly situated for a comfy environment.

in this new report they are saying there appear to be, with low odds against, up to five planets, discovered by tau Ceti..http://www.csmonitor...stance-of-Earth
But my question is,
anyone doing any conjectures or reports on, what does it take in resources and costs to try to explore or inhabit, as in life sustaining, habitations, some planet barely possible for us?

"(Do you read what they say online?) I check out all these scandalous rumours about me and Elijah Wood having beautiful sex with each other ... (are they true?) About Elijah and me being boyfriend and boyfriend? Absolutely true. We've been together for about nine years. I wooed him. No I just like a lot of stuff - I like that someone says one thing and it becomes fact. It's kind of fun." --Dominic Monaghan in a phone interview with Newsweek while buying DVDs at the store. :D

^^ You beat me to it. My Exoplanet app alerted me to this today, although they caution that the planets are unconfirmed. Still, it is very exciting.

Basically, our close neighbor tau Ceti (11.9 light years away, .78 solar masses) appears to have a five-planet system, all of the planets being Super-Earths and one of them in the habitable zone. Tau Ceti b is weighing in at two Earth masses (which I think would make it the second smallest Exoplanet yet discovered, next to Alpha Centauri B b), c is 3.10 Earth masses, d is 3.6 Earth masses, e is 4.3 earth masses and f is 6.6 Earth masses. All of these planets except f are inside the orbit of Venus, with f being just outside the orbit of Earth. e is the one that's in the habitable zone-- its slightly eccentric orbit takes it right to the inner edge, but it still looks pretty comfy. This is a pretty promising development, so I hope the data holds up.

As for exploring or inhabiting any of these worlds, it would really be useless to speculate on costs or resources-- that would be a project for an era with technology far beyond what we have now, so there would be no basis for comparison. Just to mount a robotic mission to tau Ceti would be very costly. Not for the probe itself-- we know how to build those pretty well-- but for a propulsion system that could get it there in less than thousands of years.